Korean Air, the country’s largest airline, announced Thursday it is reconsidering its orders of Boeing 737 Max 8 planes until safety concerns about the model are fully resolved.

The announcement came roughly four days after the latest crash involving a B737 Max 8 operated by Ethiopian Airlines on Sunday that killed 157 passengers and crew. It was the second crash of the same model in five months after a Lion Air flight crashed in Indonesia in October, killing 189.

Korean Air does not yet have any B737 Max 8s in its fleet, but was scheduled to take delivery of six this year starting in April.

“We were planning on using B737 Max 8s on our flight services from May, but we are now mulling whether to delay deliveries or have them delivered according to schedule but just not put them into operation until safety concerns are cleared,” a spokesperson for Korean Air said.

The spokesperson said the company is in talks with Boeing about the deliveries, adding it is hoping Boeing will come up with “adequate safety measures soon.”

In 2015, Korean Air ordered 30 B737 Max 8 planes from Boeing with options on 20 additional jets. The deliveries were to be made gradually from this year through 2025.

On Thursday, local low-cost carrier T’Way Air announced it won’t operate B737 Max 8s until the model wins back the trust of the public. It was scheduled to have four of the jets delivered this year.

Another local low-cost carrier, Eastar Jet, was the only airline in the country that had been operating B737 Max 8s. It announced Tuesday it will ground those two planes from Wednesday after consulting with the Ministry of Land, Infrastructure and Transport.

The country’s largest low-cost carrier, Jeju Air, ordered 40 of the Boeing models last year with options on 10 additional jets. The airline’s spokesperson said it hasn’t decided anything yet since the first deliveries are scheduled for 2022.

Boeing’s 737 Max 8 was one of fast-selling airplanes from the U.S. company thanks to its long flying range and high fuel efficiency.

The aircraft maker said it “continues to have full confidence in the safety of the 737 Max” in a statement Wednesday.

Despite its confidence, though, it decided to recommend to the U.S. Federal Aviation Administration a temporary suspension of operations of the entire global fleet of B737 Max aircraft “out of an abundance of caution.”

On Wednesday, the United States and Canada joined many other countries including China in grounding the controversial Boeing planes.